1. Field of the Invention
This invention relates generally to a percussion instrument in the nature of a drum having a shell-like body and a pair of elastic top and bottom drum heads stretched across the body for vibrating at a pitch level proportional to the tension produced in each of the drum heads. More particularly, the invention relates to a drum in which the pitch level in each of the top and bottom drum heads is simultaneously adjustable by simultaneous adjustment of the tension in each of the drum heads.
2. Description of the Prior Art
In one common type of percussion instrument in the nature of a drum, a pair of elastic top and bottom heads are stretched across the top and bottom of a shell-like body. The top drum head is adapted to be set in vibration when beaten by hand or with some other implement, such as a drumstick or a wire brush. Air within the drum body resonates to propagate the vibration of the top drum head to the bottom drum head. The pitch level in each of the top and bottom heads and, therefore, the pitch level of the sound produced by the drum, is proportional to the tension produced in each of the top and bottom drum heads.
Generally, the drum body is of cylindrical configuration. Each of the top and bottom drum heads comprises a circular, elastic central portion of greater diameter than the drum body and an essentially rigid outer band portion peripherally connected to the central portion. A pair of top and bottom hoops are provided to bear against the outer band portions of the top and bottom drum heads, respectively, to stretch their central portions across the top and bottom of the drum body.
Each of the top and bottom hoops is attached to the drum body by a set of circumferentially spaced, threaded tension rods that are connected to the outer surface of the drum body. The tension rods pass through a set of circumferentailly spaced bores provided in each of the top and bottom hoops. A set of nuts, provided for each tension rod, is threaded onto the ends of the tension rods and tightened against each of the top and bottom hoops. The tension, and thus the pitch level, produced in each of the top and bottom drum heads is proportional to the degree to which the nuts are tightened against the top and bottom hoops.
The adjustment of the pitch level in each of the top and bottom drum heads is a two-step process. For example, the top drum head is struck in order to ascertain the pitch level of the sound emanating from the percussion instrument, and then, each of the top nuts is alternately tightened or lossened to adjust the pitch level in the top drum head. The process is then repeated for the bottom drum head in conjunction with the bottom nuts. Often, the two-step process must be repeated several times to obtain the desired pitch level. As will be appreciated, since rotational movement must be applied to each of the nuts in order to tighten and loosen the nuts, the pitch level adjustment of such a drum is an extremely complex and time consuming process.
In another type of drum, only a single rotational movement is required for adjustment of the pitch level. In this type of drum, however, only a single drum head is used. The central portion of such drum head is stretched across a stretching wheel by a single hoop bearing against the outer band portion of the drum head. The stretching wheel is rotatably mounted on the top end of a threaded shaft. A coupling wheel, threadably engaged on the shaft, is peripherally connected to the hoop by a set of tension rod. The arrangement is such that the coupling wheel, tension rod, hoop, drum head and stretching wheel are operatively connected together for conjoint rotation on said shaft. Accordingly, selected rotation of the coupling wheel, and the operatively connected elements, serves to stretch the central portion of the drum head across the stretching wheel to adjust the pitch level in the drum head. That is, rotation of the coupling wheel is one direction increases the pitch level of the drum head and rotation in an opposite direction decreases the pitch level of the drum head. An example of such an instrument is shown in the catalog of Remo, Inc., North Hollywood, California, and marketed under the name REMO ROTOTOMS.
The simplified pitch level adjustment of a percussion instrument of the type that uses only a single drum head, as described above, has not heretofore been applied to a drum having a pair of top and bottom drum heads. In a drum that has a pair of top and bottom drum heads, the top drum head must be stretched across the top of the body, rather than a wheel, so that vibrations propagate through the air in the body to the bottom drum head. Moreover, even if by some manner of design, the top drum head could be simultaneously stretched across a wheel and the top of the body, the bottom drum head would prevent the stretching wheel from being mounted on the top end of the shaft. Still further, there is no known mechanism to simultaneously stretch and adjust the pitch level in the bottom drum head at the moment the pitch level in the top drum head is being adjusted.